V4 140 OMC Leaking crankcase - JB WELD??

Hi-<br /><br />Rebuilt my 1984 Johson V4 140 last winter and had a certain sense of pride when it started on the second crank.<br /><br />After messing around with a buch of little things, I'm on the water and happy...almost.<br /><br />My power has increased substantially - enough to warrant a higher pitched prop - that's a good thing..<br /><br />Problem is, with all of the care and planing that I put into the rebuild, somehow I didn't get the crankcase sealed properly. <br /><br />The engine runs fine at high revs - but I can't get it to idle below 1,500.<br /><br />I notice that small puffs are coming from the crankcase seal in front of the #2 piston. There is also a slight black oil streak driping down the seam of the case halves.<br /><br />I had hoped it was the bypass covers, but it's clearly not..<br /><br />My questions:<br /><br />1. Am I correct in assuming this leak is causing the rough idle?? What's the mechanism?<br /><br />2. Have any of you ever successfully fixed this issue with marine-tex or JB weld?? If so which one??<br /><br />3. I really can't see taking it all apart again, so any "short-of-that" fixed would be prefered.<br /><br />Thanks in advance

Re: V4 140 OMC Leaking crankcase - JB WELD??

What did you seal it with and was it clean? Are you positive its not the bypass cover?<br /><br />Take the cover off and look real close at the block half that meets the front half. Is it still straight? We've seen some of those areas get bent while apart and they will not reseal unless you straighten it out.<br /><br />Good luck!

Re: V4 140 OMC Leaking crankcase - JB WELD??

BTW - keep in mind that when running its pulling air on that cylinder so its running pretty lean. <br /><br />Dont want to hurt those new pistons!

Re: V4 140 OMC Leaking crankcase - JB WELD??

Thanks - I looked real hard at the bypass cover - hoping and praying that was the problem. I did remove them all during the rebuild and sealed them up good with new gaskets and compound.<br /><br />I will take one more look, but I'm fairly sure it's the crankcase seal.<br /><br />Not really thrilled to take it all apart again, especially with the short boating season here in the Northeast.<br /><br />Would you confirm the idle issues could be due to the leak?<br /><br />thanks again

Re: V4 140 OMC Leaking crankcase - JB WELD??

oops,<br /><br />I sealed it with the red stuff from loctite - i think it came from Sierra...<br /><br />adam

Re: V4 140 OMC Leaking crankcase - JB WELD??

Gel Seal is what to use. I thought I had put in in the other post.<br /><br />Sorry! Its Monday!

Re: V4 140 OMC Leaking crankcase - JB WELD??

I used Loctite 518 - from the Sierra. There book says it "replaces OMC Gel Seal 327361" and references sealing crankcase halves with it.<br /><br />Is this where I went wrong?<br /><br />Anyhow, I stipulate that I didn't do something right..<br /><br />How 'bout the quick fixes??<br /><br />I'm too busy fishin'

Re: V4 140 OMC Leaking crankcase - JB WELD??

I've used Loctite 518 on 2-stroke snowmobile engines and have never had any problems. I would guess that it wasn't clean when put together. If I were you I would take it apart and reseal that crankcase there are no quick fixes here. If you dont you may not be fishing for long.

Re: V4 140 OMC Leaking crankcase - JB WELD??

thanks -<br /><br />but I'm still looking for the duct-tape answer to get me through the season..<br /><br />The boat's in the marina, and the trailer's stowed for the season.

Re: V4 140 OMC Leaking crankcase - JB WELD??

no hackers out there?

Re: V4 140 OMC Leaking crankcase - JB WELD??

If it was me, I'd pull the powerhead, remove the intake, split the case and see if I could fix it right. You should be able to do it in about 4 to 6 hours if you've rebuilt very many. A little longer if you'renot too experienced.

Re: V4 140 OMC Leaking crankcase - JB WELD??

If a bit of crud is between the crankcase halves holding them open than your crank will be unsupported & vibrating. That can't be good for it.

Re: V4 140 OMC Leaking crankcase - JB WELD??

Give the JB Weld ah try. I'd like to know if it would work or not. Call it research.<br /><br />c/6<br /><br />Hooty

Re: V4 140 OMC Leaking crankcase - JB WELD??

Hail......What are you gonna do... JB-weld the whole seam? Since you are leaking at the worm gasket?, it will just find a new place to come out after you plug the hole or area. I guess you will have to remove the powerhead, then JB weld the case halves together all the way around, fawk it. then, if you have to open it up you can use a die grinder to cut off the jb weld, fix the problem and gather all the aluminum dust from the floor and re-apply some jb weld to that and stuff it in the cracks. OR... better yet.. you could use JB weld in place of gel seal(they sound alike so they should work)and completly seal that thang from any intrusion or internal leak. You can also jb weld the heads on without a gasket, then you won't have to worry about re-torque'n the heads!<br /><br />Just got some breaking news.. Run the engine at 4000 rpm in the driveway and let the motor injest the JB weld directly. That way you are sure to get all the leaks. It's kinda like bars leak for radiators. You can mix up a batch and sell it as "snake oil".

Re: V4 140 OMC Leaking crankcase - JB WELD??

Sparkroost-<br /><br />thanks for taking the time to reply..<br /><br />First, there's no worm gasket on this model - it's metal on metal all the way around. But I'm sure you knew that - you were just pulling our leg.<br /><br />If you were not pulling our leg, I guess you were, umm, "wrong" - that's extra funny since you were busy cracking wise about the whole thing after starting with an incorrect theory about the worm gasket..<br /><br />Thank you for your support.<br /><br />Glad I could help you giggle.

Re: V4 140 OMC Leaking crankcase - JB WELD??

Worm or no worm... it's leaking. If you plug it in one place it's likely to just weep out another. Not to mention you are going to suck and blow changing the mixture. Of course you already got that info but still that wasn't what you wanted to hear. <br /><br />You spent some time and money on that motor and you seem to be willing to scrap it and buy a new one? Sheesh!<br /><br />You asked for a "duct-tape, hackers" idea, and I gave you one. If you don't like the answer, don't post the question.<br /><br />Come on bro... JB weld.. hahahahahahhaahah

Re: V4 140 OMC Leaking crankcase - JB WELD??

Well - here's my thinking..<br /><br />I've got a 3/4 inch or so area in the seam that's spitting and bubbling. I either left a greasy thumb print at that spot or, I laid on the sealer too thin or, the case had a bad spot and I didn't check for flatness well enough.<br /><br />The rest of the case seems to be sealed fine, It's only the #2 cylinder area that broke out in this out in this small section. <br /><br />There is no question that the "right" way to fix it is to break it down and get it sealed properly. In my case that would involve a haul-out at the marina, and then 2-4 weeks while I got the time together to break it all down. (not to mention the heat from the wife as I tinkered 'til the wee hours)<br /><br />If I had a worm gasket, I would be inclined to agree with your logic that the leak would just keep spreading in both directions.<br /><br />Muffler patch is not the "right" way to fix an exhaust leak in a car, nor is that stuff they sell for gas leaks, radiator leaks and power steering leaks - but we all use them sometimes. <br /><br />We have about 6 weeks of good striped bass fishing in may/June and then again in sept./october<br />In between, it's warm water and harder work and after September the weather never seems to cooperate. I missed most of the fall run last year - after the motor died.<br /><br />With two kids, a wife, a business and a fishing habit to balance - these projects always take more time than the book rate..<br /><br />I put on the JB weld last night, if leaks now or later, we'll know it didn't work. If it fails, All I'm out is the time to remove the 1 inch stripe of epoxy when I break it down.<br /><br />It's not that I didn't like that answers given - but they were mostly theoretical "not the way I'd do it" answers. Not that I don't appreciate the input, but I was hoping to hear from someone who tried it and failed, or tried it and succeeded.<br /><br />Your "answer" seemed to be an attempt at a laugh at my expense - forgive me If I took it the wrong way..

Re: V4 140 OMC Leaking crankcase - JB WELD??

With a two stroke engine, sealing in the crankcase is critical to proper opperation, same as adding oil in the fuel, and having water going through the cooling passages. It is not merely an inconvenient leak that sputters out some oil.<br /><br />A two stroke engine uses the changing volume of the crankase to both draw air/fuel from the carb, and to charge the cylinder. With an air leak in the crankcase, you will be drawing additional air in the crankcase, and thus dilluting the carburated air/fuel mix, and hense running lean. You'll be looking at a holed or stuck piston, with related other damage to the engine.<br /><br />I don't recall where I heard the quote, but it goes along the lines of, if you don't have time to fix something right the first time, where do you plan to find the time the time to fix it when it breaks?<br /><br />That is a real tough item to work a cluge fix on, because the surfaces that need to be sealed are all coated with oil, and you'll be hard pressed to properly prep the metal, or find a material to stick.<br /><br />I feel for your situation, but would take the time to fix it right vs sticking the #2 piston, and rebuilding all over again.

Re: V4 140 OMC Leaking crankcase - JB WELD??

crankcases that are a split type as you all know are already machined to a perfect fit. no matter what the application is Dirt or a forgien material between them will not seal. If u are insistant upon using a sealer try Aviation form a gasket the type that is black smells terrible and uses a brush to apply it. Type 2 if i remember correctly comes in a greyish to silver can with an Indian chiefs head on it.

Re: V4 140 OMC Leaking crankcase - JB WELD??

I sanded and cleaned the surface multiple times with brake cleaner, being sure to blast into the seam leak. It looks good, but the real test will be upon running.<br /><br />Can this minute leak really cause a mixture so lean that the piston is in danger???<br /><br />On positive crankcase pressure, the cross-section of the leak seems so much smaller than the intake ports in the cylinder - a ratio thousands to one if I had to guess. Not knowing the volume of the crankcase cavity, its difficult to estimate the pressure build. I am assuming it's "about" 1/3 that of the cylinder compression (based on rough visual volume estimates) Does anyone know the crankcase pressure during the down stroke??<br /><br />On the Vacuum intake stroke, the leak in the seam still seems many times smaller than the idle holes in the butterfly plates (plus any other parasitic leaks) Are we sure this can cause it to run lean enough to damage the piston??<br /><br />I'm not disbelieving, just socratic learning...